AI agents use codex_modify_user to create or update resources in Sage MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Sage MCP environment.
This tool modifies user records, which is a reversible Write operation. Severity is high because modifying user accounts could affect access control, permissions, authentication state, or user identity metadata. However, it falls short of critical because the operation is typically reversible (users can be restored or re-modified) and the blast radius depends on which user attributes are modified.
From the tool's definition Tool name 'codex_modify_user' and description 'Modify a user' indicate the tool creates or modifies user data. The verb 'modify' is explicitly a Write operation that changes existing records reversibly.
Documented attack patterns abuse exactly the kind of access codex_modify_user gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Sage MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for codex_modify_user:
{
"version": "1",
"default": "deny",
"tools": {
"codex_modify_user": {
"limits": [
{
"counter": "codex_modify_user_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}codex_modify_user stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Modify a user. It is categorised as a Write tool in the Sage MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Sage MCP server in PolicyLayer and add a rule for codex_modify_user: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Sage MCP. Nothing to install.
codex_modify_user is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the codex_modify_user rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for codex_modify_user. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
codex_modify_user is provided by the Sage MCP server (sagemcp/sagemcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 359 Sage MCP tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
359 Sage MCP tools catalogued and risk-classified — across an index of 42,500+ MCP servers.